initIface* usage in plugins

Hi, I'm trying to use initIfaceLoad and initIfaceLcl to lookup core `Name`s within a plugin. My understanding is that functions such as `lookupIfaceTop` are used for this, but I'm running into an issue that I suspect is caused by some `Name`s being inappropriate for this function, so they fail with the error `Iface id out of scope: ...`. Is there a robust way to select which `Name` lookup function to use based on a core binding/expression? Thanks, Josh